They say you learn something new every day.
Here's what I learned today.

Saturday, February 03, 2007

Satellites and the Earth's Circumference

Geostationary satellites (like DirectTV) orbit the Earth about 36,000 kilometers above the equator. (NB. A geosynchronous satellite can oscillate north or south above a point on the equator. A geostationary satellite is a kind of geosynchronous satellite that doesn't move relative to the Earth.)

The circumference of the Earth is about 40,000 kilometers. Since the signal must go to and from the satellite, it travels the distance of two trips around the Earth!

Incidentally, 20,000 leagues is about 111,000 kilometers, so Captain Nemo traveled just under three times around the Earth (and not 20,000 leagues deep which would be impossible).